This invention relates to a measuring instruments for measuring the various parameters of a textile yarn, and in particular to instruments for measuring yarn parameters whilst the yarn is running through a textile machine during the processing of the yarn.
There is a requirement to measure various parameters of a textile yarn during and subsequent to the processing of the yarn, to determine the efficiency and effectiveness of such processing and the quality of the processed yarn. To this end, there are many sensing instruments available, each adapted to measure a specific parameter. A typical yarn process on POY or DTY may require the measurement of interlace, oil level and tension and the determination of the presence of broken filaments. To perform all of these measuring or sensing functions requires the use of at least three sensing instruments. Whilst some of the actual operative sensing elements may be non-contact, e.g. optical sensors, each sensing instrument requires two or more yarn contacting sensing elements and/or yarn guides to locate the running yarn in the sensor relative to the operative sensing elements. The result of adding three sensing instruments to a typical process threadline can add over 45xc2x0 of sensing element/guide wrap, thereby undesirably increasing by a considerable amount the tension in the yarn downstream of those instruments. Hence the quality of the processed yarn is often compromised by the act of monitoring its quality. For this reason, and having regard to the high process speed with some processes, it is desirable or even essential to minimise the total sensing element/guide contact with the yarn within the complete process threadline.
It is an object of the present invention to provide a yarn parameter measuring instrument which minimises the abovementioned problem.
The invention provides a yarn parameter measuring instrument comprising an inlet yarn guiding element and an outlet yarn guiding element, and a plurality of sensing devices mounted successively within the instrument, each sensing device having at least one operative sensing element adapted to be responsive to a respective yarn parameter, wherein the yarn is guided through the instrument by contact only with the inlet and outlet guiding elements and contact operative sensing elements.
The instrument may comprise a yarn tension sensing device, having an operative sensing element which may comprise a tension sensing pin. The tension sensing pin may have stress measuring means secured thereto adapted to be responsive to the deflection of the tension sensing pin due to the tension in a yarn passing therearound. The stress measuring means may comprise at least one strain gauge secured to a stem which supports the tension sensing pin.
The instrument may comprise an interlace sensing device having operative sensing elements which may comprise a laser beam generating device and a photo diode operable to receive the laser beam.
The instrument may comprise an oil content sensing device, having a first operative sensing element which may comprise a first pin to which an electrical voltage is applied and a second operative sensing element which may comprise a second pin adapted to measure the voltage on the yarn to determine the electrical resistance of the yarn between the first pin and the second pin.
The instrument may comprise, in succession, an interlace sensing device, a tension sensing device and an oil content sensing device. In this case the first pin may be the tension sensing pin, and the second pin may be the outlet guiding element.